Slug for cleaning condenser tubes



April 26, 1932. w E OBERHUBER 1,855,646

SLUG FOR CLEANING CONDENSER TUBES Filed July 3, 1928 Patented Apr. 26, 1932- WILLIAM F. OBERHUBER, or LANSDOWNE, PENNSYLVANIA, ASSIGNOR To FRANKLIN DEVELOPMENT CORPORATION, orrninnnnnrnrg PENNSYLVANIA, A. comm TION or PENNSYLVANIA SLUG OR CLEANING m m w i I Application filed July" 3,

My invention relates to slugs for cleaning condenser tubes andthelike, with particular reference to cleaning .slugs that present one or more engagement surfaces against the inside of the tube along a considerable portion of the length of the'slug.

A purpose of my invention is to make slugsof the character'indicated pass through the tubes more easily by applying a considerable 1 portion of the transmitting force to the interior of the plug near. thefront of the plug in order to avoidor reduce longitudinal compression stresses in the material of the plug along the intermediate portions of the engaging surfaces.

A further purpose is to apply fluid driving pressure near the forward end of a plug that presents to theinside' of the tube forwardly directed cleaning edges near the front and rear ends ofthe plug and of surfaces that engage the inside of the tube along a considerable portion of the plug length.

A further purpose is to provide a hollow plug with relatively staggered forward and.

rearward cleaning edges, with a fluid discharge at the forwardand readward edges,

either or both, for carrying away loosened material from the interior of the tube aheadof the plug.

A further purpose i-s'to mount a spring scraper upon the front end of a hollow slug so that the turns of the spring that engage thetube will be pulled forwardly rather than pushed forwardly. i

A further purpose is to deliver a stream-of driving fluid against the cleaning surface of a sprung mounted upon a slug so as to carry away loosened matter from in front of the slug and to act as a fluid scrubber.

A further purpose is to provide a hollow rubher slug that has a larger hollow section near its forward end' than: at its rearward end, the thicker portion at the rearward end of the slug presenting a cleaning edge to the inside of the tube and having agreater'seC- tion-a]. area to lessen the longitudinal conipression stress in this portion of the plug in-: cident to the forward push of the driving fluid exerted at the rear end of the plug. A. further purpose is to substantially limit 1928. Serial o. esaa'oz. I 1

the compression stresses in the body of. a slug to a rearward' portion-that presents a forwardly directedcleaning edge oredges against the inside surface of the tube- Further purposes will appear inthe specification and in the claims.

I have elected to showa-few forms onlyof my inventionselecting forms that are prac-- tical and eflicient inoperation and which Well illustrate the principlesi'nvolved. V

Figure 1 is a side elevation showing one form of slug carrying a scrapingspring;

F igureQ is aleft end elevation of Figure 1.

Figure 3 is an enlargedjsection taken upon w the line 3+3 of Figure 2, with the spring removed-.1

Figure dis ale-ft end elevation of the slug shown i i-Figure 1-, withthe spring removed. Figure 5 is;a section taken upon the line Figures 6 and-7v are respectively a longitudinalsideelevation and a longitudinal section of modifications. H Like, numerals refer to likeparts in all: figures. Describing in' illustration and notin limi-- tation and referring to the drawings f The slug shown inFigures 1 to .5 comprises a body 10-which is preferably solid rubber. and a scraper. spring 11 that iscarriedupon a forwardly directed nosel2 ofthe body and may desirably be; formed of spring bronze,

either of round. or. square stock.

The outside 'ofthe body is shown present- Y ing a uniformlycylindrical surfaceat 13 for some distance from the rear end, and for- Wardl-yjof the uniformly circular portion 13 as a longitudinallyflutedsurface in which arcuatefsurfaces 14:, having the same radius as the surface 13, alternate- ]with longitudinal flutes 15, the raisedarcuate surfaces 14 tapering' inwardlygat '16atthe forward end of the main portion of'the p'lug to the bottoms oft-he flutes; The'cylindrical surfaceand the front end of the ribs constitute the scraper walls.

The forward inwardtaper 16 makes the in-1 sert'ion of theslugs into the ends of tubesmore easy. Alsojwhen' the plugis hollow-the fluid pressure driving the plug through aitube eX-. pandsgthe plug radiallyuoutagainst the in:

. the nose of theplug adapts the forwardend of the body at the taper portion to expand under the driving pressure; inside. the-plug into substantial engagement with the inside of the tube, so that the: fmntof theetaper' portion may serve as a cleaning edge; and the converging end of the hollow presents a centra-lly registering seat to" afinger, stick or other suitableimplement'that may be used to pushthe slug" into'the openends'of tubes.

1 show the entranceportion ofithe hollow with a rearward flare- 19;- If desired this reanward fiare niaybeomittedP It: provides a saving; ii11the amount of rubber required for" each pl'ug and'makes theextreme rear endof the plugadapted toeasy radia lexpansion and contraction:

The reazr w-ard cylindrical portion 13 pre sents-cleaning'edges totheinsideof a 'tube at QOattiie rearends ofthe flutes v The successive t'urns' of t he spring 11 con verge forwardly and the forwardmost turn 21- has-an interior 'diameterthat is'somewliat less than the external diameter -ofth'e portion 22' of theno'se-that carries-tlie-spring. 7 I

The nose '12 comprises stepsections-progi'essively smaller" tbward' the frontg theiforw-ard'most section 23; having a diameter that readily passes theforwardmost' turn of the spring and being-- used to f pull the next sectionj 22 through the forward turn 21 ofthespring, the-spring compressing: the iaibber somewhatl. i The rearw ard end ofthe spring is bent radially; inward and extended longitudinallyrearward into a suitable-hole 24 iii the front of'theplug near the outer circumference of tlieu'earwardstep portion 25 of the nose.

The spring is thus remove-my but strongly fastened to the plug: by 1 the circumferential compression of" the front turn of the spring into the rubber tit "2'2 and bypthe seating oft-here'arwand end of the sp ring in the hole 24.

It" will be seenrthat the-nose presents a shoulder 26against the rearward side of' the forward turn of'the springiandthat when the when the slug is. passingthrough a tube the 7 shoulder 26'.

mere rearward turns ofthe, spring are in ef fect. pulled: forward .by'theforwardmost turn 21 which. is inturn pushed.- forward by the Theslugtcarnyingthespringzisconveniently 'push'd into the: end of a tube by; an implement engaging. the front end of its interior at. 18,..which stretehes the spring longitudir nsoaeae nally, making it much easier to enter the slug.

One of the principal objects of my invention is to lessen heavy friction between the inside ofthe tubesand'portions of: the outside surfaces of the slug that are some distance rearwardly from the forwardly presented edges of the same surfaces V I do this "by lessening or preventing longitudinal'compression-stressesixrthe portion of the circumferential wall of'the' slug'that is rearward of. these edges, the cleaning action of'the slug surfaces being most effective at the forwardly. presented edges and least effective at portions of the surfaces that are rearward of the:foravardiedgesq The engagement? betweenv theinside of the tube andrportions ofzthezslngsurfacethat are relatively re arwardly; distantfroma the cleaning edge 1138 1111 thepastim'ade: the-slugs unduly hard to pass through:the-ntubesgwithoutz making their; cleaning action. better to; any extent". that is at all. comparable with the. greater fluid pressureneeded' to drive the slugs through-the tubes.

When a; slug .isd'rivi'ng through aatilbe the, forces actingrupon itcomprise drivingzforces efiectiveacross the; areai of the tube to; force:

the slug along through the tube an deresistant forces efiective on the portion. or; portionsof, the circumferential surface of thefslugthat engages or: engage the: 11151118} of theatube...

The total: driving force upon the slugs is; I equahtm the. sectionaL area: of the: tubemulti-- pliedsby the difference between the fiUid;p1eS sureback of the. slug'and that aheadof the slu I In the; hollow slugshown in Figure 8, a

major. portion; of this totalzdrii ing force is.- appliedz inside-the slug; near-the: forward; end; ofathexbody'portion, t-h atni's,-.up on that portion: thereof: thatis inlfront. of; the largest diameter'at 17,,and as arresult'the; longitudinal: compression in the portion of the plug; that ill lUii

isrearwardiofthisdiameteris diminishedby th'ezpresence of 'the'hollow, by. an amount that is;equaltothezforcethat is applied ahead of thisidi'ameter.

' It will be seen that the area-of= the hollow portion will be increased; somewhat by internal: expansion": due to the-fluid pressure insidethehollow', and that this expansion results in compression; radiallycutward against the inside of the; tube; and thisv increase in sectional area may be quite material; at the forward end of; the flutedsection-if, as in Figures 1 to: 3,jt-heraised portions forwardly taper. a a Y The resistance presented by the inside .of the tube; to theoutside, of the, slug will be ofiered' wherever the slug-presents contact to: the tube, which is over the whole outside surface of the cylindrical portion '13, particularly at the forwardly directed cleaning The fluted portion ahead of the circular portion 13 may be eitherunder longitudinal compression, longitudinal tension, orwithout longitudinal stresses of eithertension orj compression. according to the relation between the resistance presented by the inside of the tube to the abovedifl'erent portions of the plug surface, and of the relation-of the size of the hollow at 17 to the total area of the tube back of the-plug.

, In practice, I prefer to have the fluted portion of the plug ahead of thecircular portion 13 under more or less longitudinal tension in order to more. greatly reduceithe tendency for the arcuate surfaces 14 to bulge along their length (particularly near the middle of their length) during passage through a tube, the .tendencyto bulge being due to friction along the length of the engagv ing surfaces withf'a heavy driving pressure applied to the plug rearwardly of these surfaces. 7 I provide the for'wardend of theplug with perforati0ns-27 directed diagonally outward at the front end of the fluted portion of the body. V

These perforations pass a stream 'of'driving fluid which carries away loosened matter from in front of the plug, the fluid shooting through these perforations at a velocity greatly in excess of that of theiforwardly moving slug. 7

When the condition of a tube is such as to make it advisable to use aspring, the driving fluid is usually water and the escaping streams of water from the perforationsfll"- serve not only to carry away the loosened-par-- ticles from in front of the slug but alsoImake the cutting action of the spring'more effec-.

tive.

In'the form of Figure 6 I make provision for the passage of driv ng fluidalong the out side of the slug by longitudinally fluting the exterior surface of the slug at 28. a

The forwardlydirectedcutting edges 20 here extend directly across the rear ends of the flutes 15 of the forward portion of the slug,

and I have not provided anyinward taper on the front of the arcuate surfaces 14 (such as 16 of Figure '1) but have extended the hollow? interior further rearwardly so that the largest diameter 17 of the hollow is butzslightly to the rear of the cleaning end edges 29 presented by the forward fluted section; -VVith this arrangement the cleaning edges 29 at the front of the forward fluted section are pressed tightly against the inside surface of the tube by the internal expansion from within-the hollow, and the driving force back of this point is so small that the tube portion intermediate the cleaning scraping f edges 29 and 20 is normally under longitudinaltension stress though under radial outwardcompression stress against the inside of. the tube." I

r I have provided perforations 27: similarto the; perforations 27 .of Figure 3 so that driving fluid shoots out ahead of the 'mov; p .ing slug, fromboth along the diflerent flutes outside the slugand from inside the slug through the perforations 27', and very effeetively. carries away loosened particles from in front of the different cleaning edges. 7

I have made the forwardly converging end 30 of the hollow interior of the plug, substantially the same as in Figure 3 and when-inserting these slugs into tubes, engage the slug at the axis at the front end of the hollow portion at 31 so that the plug is effectively pulled intov the open end of a tube by reason of the push upon the hollow portion at 31.

When the slugs are driven through the tubes with, compressed'air they fly out the ends of the tubes and against thecondenser wall that is normally in front of the tubes.

Hitherto they have struck the condenser. wall head-on with a'force that has injured the slugs to an extent that has materially shortened their life, and one of the objects of my invention is". to avoid these injurious head-.

, on impacts of the slugs against the condenserwall bylmaking the forward end of the nose of the slug ofi' center with respect to the slug axis. a

The impacts are only injurious to any considerable extent if the slug strikes squarely upon" its end, and in Figurefi I have providedan, offset nose that presents its for Ward nd 32 well to one side of thezcentral,

axis of the slug.

This forward end engages the wall of the condenser and deflects the sluglaterally, pres venting the squarely head-on impacts with the Walland in effect to great extent breaking the force of the impacts.

In this way I avoid theldirect impacts in i line with the axisof the slugsthat have in the past resulted in shortening the slug life.

In Figure 3 I have made the hollow portion with uniform divergence from its, section of minimum diameter to that of largest diameter at. 17 while in Figuref fl I show the hollow asmade upof two cylindrical 1portions33 and 34', and the forwardly convergingportion 30 that extends into. the nose for proper regis-. tering' the tool used for pushing the slug into the tube.

The exact manufacture.

' The longitudinal stresses in the circumferential wall around the'holl'ow whether the form of interior is somewhat a matterof ndividual preference, and ease of of the body of the slug, a cleaning spring mounted upon the nose at an intermediate section, the forward turn of the spring compressing into the intermediate section and the turns of the spring extending rearwardly being successively larger, the rearward turn being adapted to engage the inside of the tube and having the end of the spring inserted into the body of the slug near the circumference, and the slug having a hollow frglm the rearward end to near the forward en 8. A rubber slug for cleaning condenser tubes, hollow forwardly from its rear end to near its forward end and having a larger internal diameter near its forward end than -near its rearward end.

9. A rubber slug for cleaning condenser tubes, forwardly hollow from its rearward end to near its forward end, and the hollow having a larger internal diameter near its forward end than near its rearward end and having a forwardly converging forward end.

10. A rubber slug for cleaning condenser tubes having longitudinally extending ribs, said slug being hollow from its rearward end to near its forward end, and the hollow near its forward end and in the neighborhood of the front ends of the ribs having a sectional area greater than half the total sectional area of the slug. 7

11. A rubber slug for cleaning condenser tubes hollow forwardly from its rearward end to near its forward end, and having, outside of the hollow, forward and rearward scraper walls, the hollow having a greater inside diameter at the forward scraper wall than at the rearward scraper wall.

12. A rubber condenser tube slug, hollow from its rearward end toward its forward end and having a spring mounted upon the front of the slug adapted to be dragged upon the front end of the slug but removable therefrom and engaging the walls of the condenser tube to the rear of the front end of the hollow in the slug.

13. A rubber slug presenting a succession of forwardly directed cleaning edges and projection and a spring mounted upon the "tubular projection and engaging the slug wallsto the rear of the front end of the hollow.

15. Ina water-driven slug for cleaning condenser tubes, a spiral cleaning spring, .a hollow rubber slug connected with the spring at the front end of the slug and the smallerpartof the diameter of the spring, the slug beingv apertured to deliver water in proximit p to the line of engagement between the part a o the spring of largest diameter and the condenser tubes to give a scrubbing action,

e 16. A composite slug comprising a rearwardly hollow rubber body adapted to seal against a tube at its rear end and having spaced. ribs forwardly directed from said rear end'and adapted to engage the tube and forwardly directed fluid passages near the V rearward end of the slug, and presenting a succession of other forwardly directed cleaning edges and intermediate water passages toward its forward end, the cleaning edges near the forward end being staggered with respect to those near the rearward end and the slug hollowed out from the rear, said hollow having a larger internal diameter near its forward end than near its rearward end so as to effectively apply the larger portion of the driving force near the forward end of the slug and longitudinal tension stresses between the forward cleaning edges and the rear end of the slug.

14. A rubber slug hollow from the rear to near the front end of the slug, a tubular 

